Well, you are not only invisible for others, you can't see your body either. Imagine failing to block an attack because you don't see your leg where is heading to lmao.
The suit does not give more durability, it is flexible, they are clothes. The impact of any attack Sanji would feel them with his own body, he needs his own durability to tank the attacks. Suit gives the extra of being resistant enough so for cutting/piercing attacks it can stop the pierce, that's true, but not the impact/energy behind those attacks. And anyway, Sanji can take those kind of attacks with his Armament. The shield cape is the only thing that gives actual durability.
Enma does not give greater strength, a sword power depends on its user power. Enma's power up consisted on Zoro's training his Armament Haki. Armament = power and defense. That is above suit's "durability" or power increase. Haki is a more efficient way to boost your power and defense than Germa's technology.
And Sanji's invisibility probably will have some sort of limitation, Oda does not give good abilities without a handicap or some kind of limitation for free.
So their PUs are similar.